The present invention relates to an improved elastomer seal in which the elastomer is energized in two stages. The improved seal structure of the present invention has particular applications to annular seals between members such as hanger packoff seals.
U.S. Pat. No. 4,008,898 discloses an annular elastomer seal between facing cylindrical surfaces in which the seal follower or actuator is shear held inactive by a shear pin and the seal support ring is also shear pinned so that the initial seal loading results from the movement of the seal follower and then when the seal exerts sufficient load on the seal support ring it moves downward in the annulus to let the seal move to its desired sealing position.
U.S. Pat. No. 4,138,144 discloses another wellhead annular sealing assembly in which shear pins are used to control the time of movement of the first member 40 and the locking sleeve 50.
U.S. Pat. Nos. 4,407,530, 4,408,783 and 4,416,472 are all directed to an annular packoff for a hanger in which the seals are controlled to be set singly and in series.
U.S. Pat. No. 3,004,776 discloses a sealing nut for a pipe coupling having a press ring 15 carried by the nut by a thin section which is intended to be sheared so that the press ring and the sleeve both exert sealing force on the resilient sealing ring. Press ring and sleeve coact to contain sealing ring within nut and around the exterior of pipe-end threads 19.